Containers used to retain or store various temperature and/or pressure sensitive substances such as, for example, aqueous solutions, peroxides, chlorines, alcohols, aromatics, ketones, or other chemically active substances, or that are subject to changes in pressure, temperature, altitude and other factors affecting packaging conditions require venting to avoid the negative effects that can result from retaining such sensitive substances in a container. Failure to vent the container and/or inadequate venting thereof may result in a pressure differential between the inside of the container and the outside of the container. This pressure differential may in turn cause the container to collapse, swell and/or leak.
Various venting arrangements have been developed in an effort to reduce or eliminate the negative effects associated with poorly vented containers. For example, it is known to utilize hydrophobic membranes as gasketing elements allowing for the passage of various gases to increase and/or decrease the pressure inside of a container while simultaneously providing a seal for containing a liquid. U.S. Pat. No. 6,602,309 to Vizulis et al. (the “Vizulis '309 patent”) and U.S. Pat. No. 3,951,293 to Schultz (the “Schultz '293 patent”), each disclose membrane gasketing elements utilized for vertically venting internal pressure differences of a container. The Vizulis '309 patent discloses a gasketing element or liner having a fluid impermeable layer, a foil layer, a sealing means and a vent patch fixedly attached to a surface of the sealing means for covering a vent hole extending vertically through the liner. The Schultz '293 patent discloses a hydrophobic liner having a film of unsintered tetrafluoroethylene that is supported across a container opening by a perforated sealing diaphragm.
It is also known to utilize a polytetrafluoroethylene (PTFE) liner or an expanded polytetrafluoroethylene (ePTFE) liner as a gasketing element in vertical venting arrangements. PTFE and/or ePTFE liners have a microporous structure that is suitable to repel liquids while safely allowing for the free passage of air or gas to maintain equilibrium in a closed container. These liners typically either cooperate with a venting aperture located in a cap above the liner or have a number of grooves or channels in an upper surface of the liner that cooperate with the threads of a cap to vent the container.
Certain shortcomings associated with the above noted venting arrangements include the limited venting capacity provided by the constrained size of the venting aperture and/or the liner channels and the deficient mechanical properties often associated with the materials utilized in the gasketing element. For example, conventional PTFE can spread out under compressive loads, thereby reducing its ability to provide an effective seal over time. Also, although ePTFE is typically of a higher strength than conventional unexpanded PTFE, it is believed that even further improvements are possible, for example, to ease processing requirements and/or to achieve other desired properties for different gasketing applications. See U.S. Pat. No. 5,964,465 to Mills for a discussion on some of the short comings associated with PTFE and ePTFE.
Accordingly, it is an object of the present invention to provide a solution to one or more of the above noted shortcomings of the prior art. It is a further object of the present invention to provide an improved gasket and method of horizontally venting containers with gaskets.